In recent days, letters from Theresa May have been landing on the doormats of Conservative Party members across the country - trying to win them over to her vision for Brexit.

The mailshot, seeking their backing for the proposals agreed at Chequers last month, also features positive messages from ministers and other big hitters in the party endorsing the package.

The proposals for how the UK can trade with the EU after Brexit have certainly proved controversial at Westminster, with several ministers quitting in protest.

So what do Tories at grassroots level think about it all?

"I am well aware of the strong feelings members of our party have on this important national issue," Mrs May writes.

And it is not hard to find frustrated members.

In the Wycombe constituency, represented by former Brexit minister Steve Baker, a survey found 78% of members were against what has become known as the Chequers plan.

The vice-chairman of the local Conservative Association, Peter Ward, resigned over the issue.

He says he will not campaign for a party that is "betraying" Leave voters.

"If I'm not happy with it, I can't then knock on doors and tell people, 'please carry on supporting us' if this is a complete sell-out," he says.

Key to the objections has been a free trade area for goods based on a "common rule book" with the EU, and a "combined customs territory" covering the UK and the EU - unhappy Eurosceptics say this means the UK will still be bound by EU rules.

Mrs May seeks to address this in her letter to activists - she says her long-stated red lines remain intact, with Britain leaving the single market and customs union and ending freedom of movement.

"We will take back control of our money, laws, and borders, and begin a new exciting chapter in our nation's history," she says, adding: "I know that some people are concerned that this common rule book will stop us doing trade deals. I can assure you this is not the case - and I would not be proposing it if it would."

'Express train for Corbyn'
But another member in Wycombe, Tom Pike, is worried the plan will hurt the Conservatives at the ballot box.

"My concern about Chequers is that it's possibly like a high-speed, express train for Jeremy Corbyn into Downing Street," he says.

The grassroots activists in Wycombe are not alone.

The Conservative Home website carried out two readers' surveys, one straight after Chequers, the other the following week. Both showed strong opposition to the prime minister's plan.

Conservative Home executive editor, Mark Wallace, says it is striking that loyal activists are not wholly convinced.

"Try as I might I cannot find really anybody who is actively enthusiastic about it," he says.

"If people's best response is some grudging acceptance with uncomfortable doubts, that is not a good position for the government to be in."

Speaking to chairmen of local Conservative Associations provides a mixed picture.

While some say the plan is not a genuine attempt to take the UK out of the EU, others think it is important to back the prime minister.

Briefings that were arranged for local association chairmen at Downing Street last month appear to have put minds at rest.

The deputy chairman of North East Bedfordshire Conservatives, Richard Wenham, campaigned for Leave but says he accepts the need for compromise.

"I'm realistic that when we look at the result of the country it was pretty much split 50-50, so we have to find a way forward that will allow us to take the whole country with us and also find something that is acceptable to Parliament," he says.

'Tough job'
Emma Lane was, until a month ago, the chairwoman of New Forest West Conservative Association. She says the prime minister has her full backing: "My constituency is very strongly blue and we are very supportive of Theresa May.

"She is a very strong-willed and very strong-minded woman and I think she has a very, very tough job."

On the other side of the argument, campaigners have launched a new Twitter hashtag, #standup4Brexit, this week.

One of the main players is the Worcestershire-based activist, Paul Everitt-Clay. He thinks some officials may be hiding their true feelings.

"I can think of three specific examples where the chairs have actually gone on record that they support the Chequers plan, but when you have a private conversation with them, they actually have an alternate view," he says.

Despite the criticism of Mrs May's plans, I found activists calling for her to be replaced to be few and far between.

Chequers critic Mr Pike adds: "We're not in an ideal position at the moment, but going into a really brutal leadership fight is absolutely the worst thing for Britain and our party at this moment."